1. Field of the Invention
The present invention relates to a mobile station apparatus of a mobile communication system and in particular, to a mobile station apparatus capable of simplifying cell shift processing and handover processing in a communication state.
2. Background Art
In a mobile communication system, signal transmission and reception are wirelessly performed between a base station apparatus and a mobile station apparatus.
FIG. 6 shows an example of the configuration of a mobile station apparatus which is a mobile radio communication terminal, for example, in a mobile communication system in the related art.
The mobile station apparatus in this example includes a radio section 101, a cell search section 102, a radio quality measuring section 103, a baseband modulation and demodulation section 104, a report information acquisition section 105, a cell selecting section 106, an application data transmitting and receiving section 107, and a main controller 108.
The radio section 101 transmits and receives communication signals between the base station apparatus and the mobile station apparatus and performs band conversion between a signal in a radio frequency band and a signal in a baseband.
The cell search section 102 performs cell search processing, such as identification of a cell and detection of a path, from the signal converted into a baseband signal.
The radio quality measuring section 103 measures the radio quality (for example, RSCP (desired power of a received wave per code channel) or Ec/Io) of a service cell or an adjacent cell.
The baseband modulation and demodulation section 104 performs baseband demodulation processing on the signal converted into a baseband signal and baseband modulation processing for transmitting the data to a network side through the radio section 101 and the base station apparatus.
The report information acquisition section 105 acquires the report information, which is transmitted from the network side through the base station apparatus, among the data subjected to the baseband demodulation processing.
The cell selecting section 106 selects a cell to be connected to, selects a cell to shift to, and selects a cell to be added by diversity handover, for example, using the report information acquired by the report information acquisition section 105 and the radio quality measured by the radio quality measuring section 103.
The application data transmitting and receiving section 107 performs transmission and reception of the data (for example, user data) according to the communication application executed by the mobile station apparatus in this example.
The main controller 108 executes call processing and the like as a mobile station apparatus while performing overall control of the respective sections of the radio section 101 to the application data transmitting and receiving section 107.
Next, an example of operation performed by a mobile station apparatus of a mobile communication system in the related art will be described.
Here, the case where a service cell does not exist or the case of an operation in a standby state (in this specification, a mode in this case is called an idle mode) and the case of an operation during communication (in this specification, a mode in this case is called a communication mode) will be separately described.
An operation in the idle mode will be described.
When a mobile station apparatus is out of a service area, a frequency in the radio section 101 is set and the cell search section 102 starts cell search processing. If there is an effective signal in the frequency set in the radio section 101, it is detected as a connection candidate cell by the cell search section 102. As a method of determining an effective signal, for example, a method may be considered in which it is determined to be effective when a quality measurement result in the radio quality measuring section 103 regarding a detection signal (candidate cell) is equal to or larger than a predetermined threshold value.
Then, the baseband modulation and demodulation section 104 receives a signal of a connection candidate cell, and the report information acquisition section 105 acquires the report information regarding the candidate cell. When it is determined to be a connectable cell from the analysis result of the report information acquired by the report information acquisition section 105, the state transitions to the “service area”. On the other hand, when there is no effective detection in the cell search section 102 or when it is determined that it is a cell under construction or it is not a connectable cell because it belongs to other service providers, for example, from the analysis result of the report information acquisition section 105, a next frequency is set in the radio section 101 and the above operation is repeatedly performed until the mobile station apparatus transitions to the “service area”.
When the mobile station apparatus is in the service area, the cell determined to be a “connectable cell (station)” is set as a service cell, and the radio quality of the service cell is periodically measured using the radio section 101, the cell search section 102, and the radio quality measuring section 103. Moreover, on the basis of the “adjacent station information” in the report information regarding the service cell acquired by the report information acquisition section 105, the radio quality is periodically measured similarly using the radio section 101, the cell search section 102, and the radio quality measuring section 103. If the cell selecting section 106 determines that the quality of an adjacent cell is better than the quality of the service cell during the periodic measurements, the mobile station apparatus shifts from the service cell to the adjacent cell.
An operation in the communication mode will be described.
In the communication mode, a frequency of the service cell is set in the radio section 101, the baseband modulation and demodulation section 104 performs transmission and reception of a signal of the service cell, and the application data transmitting and receiving section 107 performs communication with the network side while performing transmission and reception of the application data. Also in the communication mode, a search operation is performed in preparation for deterioration of the radio quality of the service cell. Although this search operation is the same as that in the idle mode, handover processing or shift of the service cell is executed as a result of search processing. According to the shift of the service cell, the report information regarding a new service cell is acquired and processing in the communication mode is continuously executed.    JP-A-2007-243878 discloses the related art.
Regarding a mobile station apparatus of a mobile communication system in the related art, problems of the operation in the related art will be described.
In the idle mode, especially when a mobile station apparatus is within a service cell, for example, all adjacent stations notified through the report information are searched for in a sequential manner in the related art. If an effective cell exists at the beginning of adjacent station setting, the adjacent station can be detected in a short time. However, if an effective cell exists at the final stage of the adjacent station setting, it takes too much time for the effective cell to be detected.
Similarly, also in the communication mode, all cells registered in adjacent stations of the report information regarding a service cell should be searched for. Therefore, it takes too much time to search for an adjacent station.